Early data recently hinted that if a pregnant woman catches COVID-19, her newborn can pick up any immunity to the infection inside the womb. However, there are still many questions until now.
In new research published on January 29 in the JAMA Pediatrics journal, researchers examined blood samples from over 1,470 pregnant women, 83 of whom, according to ScienceAlert, "tested positive for antibodies SARS-CoV-2, the coronavirus that causes COVID-19," during delivery.
Umbilical cord blood samples were taken from most babies born to these women. They also had a positive result for antibodies, proposing that babies picked up the said passive immunity.
The amount of antibodies passed to the newborn greatly relied on the quantity and type of antibodies present in the mother and when she got infected with COVID-19 while pregnant.
Longer Time of Antibody Transfer
"The longer [the] time between maternal infection and delivery, the greater the antibody transfer," study authors Dr. Karen Puopolo and Dr. Scott Hensley of the University of Pennsylvania Perelman School of Medicine wrote in an email.
This connection held true if the mother developed COVID-19 stayed asymptomatic during the infection. The transferred antibodies may offer protection to the infant. However, work remains to be done to identify what antibody types and levels are needed to shield newborns from COVID-19 infection, not to mention the duration of such antibodies in the newborn circulation, explained by the authors.
Another major question now, the scientists added, is how well the transferred antibodies are neutralizing the virus, blocking its capability to infect cells.
According to the Houston-based Baylor College of Medicine's associate professor of pediatric infectious disease, Dr. Flor Munoz-Rivas, it is "hopeful to have this data."
Munoz-Rivas, who was not part of this new study, added that by studying antibody transfer following the natural infection of COVID-19, they could gather clues about vaccines administered to pregnant women and offer the same protection to newborns.
In this new research, the study authors specifically tested for antibodies that fasten onto the coronavirus spike protein, a structure sticking off the surface of the virus; the antibodies the research group "looked for all target the 'receptor-binding domain or RBD," the spike part that binds straight to the receptor, or doorway, into cells.
Previous reports found that RBD antibodies are most crucial for neutralizing the coronavirus. However, not all RBD antibodies, Munoz-Rivas explained, can cross the placenta.
That is due to the fact that the placenta enables only specific antibodies through the use of a special receptor and protein that transfers antibodies into the organ.
Essentially, only small, Y-shaped antibodies, also known as immunoglobulin G or IgG, can be suitable for the receptor so they solely can reach the fetus and offer immune protection.
Not All Babies Get Protected
The study also specified that not all babies get protected. Specifically, out of 83, 72 babies are born to antibody-positive mothers who had IgG present in their cord blood and the general amount associated with IgG concentrations in their mother's blood.
Meanwhile, the rest of the babies, 11 of them, who tested negative for the antibodies did so for a couple of reasons.
Six of their mothers had relatively low IgG levels, suggesting that they were possibly very early in their infection that there had not been time for them to generate and transport antibody across the placenta, explained the authors.
Or, the mothers generated lesser antibodies compared to the average, although this is a less possible scenario, they also said. The other five babies' mothers only tested positive for the IgM antibodies, which cannot cross the placenta.
RELATED TOPIC: UK May Be the First Country to Authorize COVID-19 Vaccine